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本文主要解析一下apache common pools下的GenericObjectPool的参数设置
GenericObjectPool
commons-pool2-2.4.2-sources.jar!/org/apache/commons/pool2/impl/GenericObjectPool.java
public class GenericObjectPool<T> extends BaseGenericObjectPool<T>
implements ObjectPool<T>, GenericObjectPoolMXBean, UsageTracking<T> {
//......
}
默认配置见
commons-pool2-2.4.2-sources.jar!/org/apache/commons/pool2/impl/GenericObjectPoolConfig.java
public class GenericObjectPoolConfig extends BaseObjectPoolConfig {
/**
* The default value for the {@code maxTotal} configuration attribute.
* @see GenericObjectPool#getMaxTotal()
*/
public static final int DEFAULT_MAX_TOTAL = 8;
/**
* The default value for the {@code maxIdle} configuration attribute.
* @see GenericObjectPool#getMaxIdle()
*/
public static final int DEFAULT_MAX_IDLE = 8;
/**
* The default value for the {@code minIdle} configuration attribute.
* @see GenericObjectPool#getMinIdle()
*/
public static final int DEFAULT_MIN_IDLE = 0;
private int maxTotal = DEFAULT_MAX_TOTAL;
private int maxIdle = DEFAULT_MAX_IDLE;
private int minIdle = DEFAULT_MIN_IDLE;
//......
}
pool基本参数
基本参数
- lifo
GenericObjectPool 提供了后进先出(LIFO)与先进先出(FIFO)两种行为模式的池。默认为true，即当池中有空闲可用的对象时，调用borrowObject方法会返回最近（后进）的实例 - fairness
当从池中获取资源或者将资源还回池中时 是否使用java.util.concurrent.locks.ReentrantLock.ReentrantLock 的公平锁机制,默认为false
数量控制参数
maxTotal
链接池中最大连接数,默认为8maxIdle
链接池中最大空闲的连接数,默认也为8minIdle
连接池中最少空闲的连接数,默认为0
超时参数
- maxWaitMillis
当连接池资源耗尽时，等待时间，超出则抛异常，默认为-1即永不超时 - blockWhenExhausted
当这个值为true的时候，maxWaitMillis参数才能生效。为false的时候，当连接池没资源，则立马抛异常。默认为true
test参数
- testOnCreate
默认false，create的时候检测是有有效，如果无效则从连接池中移除，并尝试获取继续获取 - testOnBorrow
默认false，borrow的时候检测是有有效，如果无效则从连接池中移除，并尝试获取继续获取 - testOnReturn
默认false，return的时候检测是有有效，如果无效则从连接池中移除，并尝试获取继续获取 - testWhileIdle
默认false，在evictor线程里头，当evictionPolicy.evict方法返回false时，而且testWhileIdle为true的时候则检测是否有效，如果无效则移除
检测参数
- timeBetweenEvictionRunsMillis
空闲链接检测线程检测的周期，毫秒数。如果为负值，表示不运行检测线程。默认为-1.
commons-pool2-2.4.2-sources.jar!/org/apache/commons/pool2/impl/GenericObjectPool.java
public GenericObjectPool(PooledObjectFactory<T> factory,
GenericObjectPoolConfig config) {
super(config, ONAME_BASE, config.getJmxNamePrefix());
if (factory == null) {
jmxUnregister(); // tidy up
throw new IllegalArgumentException("factory may not be null");
}
this.factory = factory;
idleObjects = new LinkedBlockingDeque<PooledObject<T>>(config.getFairness());
setConfig(config);
startEvictor(getTimeBetweenEvictionRunsMillis());
}
commons-pool2-2.4.2-sources.jar!/org/apache/commons/pool2/impl/BaseGenericObjectPool.java
/**
* The idle object evictor {@link TimerTask}.
*
* @see GenericKeyedObjectPool#setTimeBetweenEvictionRunsMillis
*/
class Evictor extends TimerTask {
/**
* Run pool maintenance. Evict objects qualifying for eviction and then
* ensure that the minimum number of idle instances are available.
* Since the Timer that invokes Evictors is shared for all Pools but
* pools may exist in different class loaders, the Evictor ensures that
* any actions taken are under the class loader of the factory
* associated with the pool.
*/
@Override
public void run() {
ClassLoader savedClassLoader =
Thread.currentThread().getContextClassLoader();
try {
if (factoryClassLoader != null) {
// Set the class loader for the factory
ClassLoader cl = factoryClassLoader.get();
if (cl == null) {
// The pool has been dereferenced and the class loader
// GC'd. Cancel this timer so the pool can be GC'd as
// well.
cancel();
return;
}
Thread.currentThread().setContextClassLoader(cl);
}
// Evict from the pool
try {
evict();
} catch(Exception e) {
swallowException(e);
} catch(OutOfMemoryError oome) {
// Log problem but give evictor thread a chance to continue
// in case error is recoverable
oome.printStackTrace(System.err);
}
// Re-create idle instances.
try {
ensureMinIdle();
} catch (Exception e) {
swallowException(e);
}
} finally {
// Restore the previous CCL
Thread.currentThread().setContextClassLoader(savedClassLoader);
}
}
}
- numTestsPerEvictionRun
在每次空闲连接回收器线程(如果有)运行时检查的连接数量，默认为3
private int getNumTests() {
int numTestsPerEvictionRun = getNumTestsPerEvictionRun();
if (numTestsPerEvictionRun >= 0) {
return Math.min(numTestsPerEvictionRun, idleObjects.size());
} else {
return (int) (Math.ceil(idleObjects.size() /
Math.abs((double) numTestsPerEvictionRun)));
}
}
minEvictableIdleTimeMillis
连接空闲的最小时间，达到此值后空闲连接将可能会被移除。默认为1000L * 60L * 30LsoftMinEvictableIdleTimeMillis
连接空闲的最小时间，达到此值后空闲链接将会被移除，且保留minIdle个空闲连接数。默认为-1.evictionPolicyClassName
evict策略的类名，默认为org.apache.commons.pool2.impl.DefaultEvictionPolicy
public class DefaultEvictionPolicy<T> implements EvictionPolicy<T> {
@Override
public boolean evict(EvictionConfig config, PooledObject<T> underTest,
int idleCount) {
if ((config.getIdleSoftEvictTime() < underTest.getIdleTimeMillis() &&
config.getMinIdle() < idleCount) ||
config.getIdleEvictTime() < underTest.getIdleTimeMillis()) {
return true;
}
return false;
}
}
这里就用到了上面提到的两个参数
